Hi! Folks,
A recent article in The New York Times, which was brought to my attention by a friend, as I never read newspapers (something I have in common with my hero Tim Ferriss), addresses an issue of real interest to endurance athletes. When to workout in relation to food intake? I think that the best way to address this issue is to think about what you are trying to achieve in relation to the dynamic nature of your food stores. Basically, energy is provided in the form of food as carbohydrates, fats and proteins. Once your food is digested, short-term energy storage is provided in the form of liver (for the whole body) and muscle (for muscle) glycogen. Once you deplete liver glycogen, which maintains blood glucose levels in the insulin active state, blood glucose levels fall and you move into the glucagon active state, and then gluconeogenesis (making new glucose) takes over the glucose supply process. Gluconeogenesis occurs largely in the liver and kidneys, and it provides glucose needed largely for the maintenance of erythrocyte (100%) and brain (20%) energetic activities. The glucose generated in this way is made from proteins using energy derived from fat. The use of proteins then starts to burn away your muscles and blood white cells (nothing is free!). Basically, when you are running on liver glycogen you are in a very different metabolic state to when you are running on gluconeogenesis. Exercising before breakfast, when liver glycogen is depleted, will necessitate the burning of fat, as promoted in the article in The New York Times. However, for endurance training you will have to start eating (for me it is chocolate Power Bars on the bike and Hammer Gel on the run) when you deplete liver glycogen in order to avoid ‘bonking.’ For the endurance athlete a better approach to bioenergetic regulation is to increase mitochondrial mass to optimize the use of liver glycogen during exercise, and to maintain this critical store of energy for as long as possible. So! Running before breakfast without eating might be great for weight loss but it would be the wrong training process. Workouts designed to increase mitochondrial mass was the strategy used by my coach Chris Hauth to great effect in my last Ironman. Thanks Chris!
It all comes down to understanding basic bioenergetics, for which I strongly recommend Harper’s Biochemistry. It is very readable for a Biochemistry book!
Cheers,
KevinImportant Note: These posts do not provide medical advice. You should always consult your physician before undertaking or significantly modifying an exercise program.
Copyright © 2010 Kevin T. Morgan aka FitOldDog, Old Dogs in Training, LLC.
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